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Building a Controls Test Board

Hello Everyone!

I am new here, but I have looked through the forums and done some research before writing this and I think I have a handle on what is involved. I just wanted to pick your brains on a few items before getting started.

Background:

We are a test and balance company and we deal with numerous controls systems (upwards of 15) on a regular basis. We do the best we can to have our guys trained on connecting and operating each system, but we are constantly running into communication issues and it is becoming a costly problem. The solution that we are proposing is to build a controls board in our office with multiple manufacturers / topologies. This should allow our technicians to verify that their computer can connect to a particular system prior to sending them to the job site. This would also allow us to avoid bugging the controls folks with random issues.

Details:

At the moment, I have ebay'ed 5 controllers that we use often: TAC MNL-V1R3, Carrier CCN VAV controller with Terminal board and actuator, Trane Varitrane UCM 4.2, JCI Metasys VMA-1420 and a Honeywell W7751E1007. I would also like to get a Trane Comm 5 board as well, but we don't really have issues connecting to those (for the most part).

Each controller will be setup independently and we hope to have actuators on all of them (those that don't have one built in that is). I was also toying around with the idea of hooking up an air pump with a pressure regulator to supply a pressure to the airflow tubing on the transducers at each board. That way our guys can see the airflow and calibrate the sensors and play around some more. Also, since the controllers are used, I believe most will have a program setup in them already so that makes life easier on us non-programmer types.

So that covers us for LON, CCN, and RS-485 comms on several different platforms.

My Questions:

I need to work out a power solution for the controllers. Please keep in mind that I'm not very familiar with this side of things. Is it possible to use 1 class 2 transformer to power multiple controllers (not all of them, but 2 or 3) and are there any problems that may be associated with doing this? From what I understand, if the controllers have a load of around 20VA each, then a 40 VA transformer could supply 2 controllers. Am I thinking about that correctly? If so, how do I determine what the minimum VA load is for each controller? Would this come from product data / installation manuals?_

Does anyone have any tips or suggestions for what works best when building a board such as this?_

Does anyone have any photos of a board in their shop that I could reference (just to get ideas)?

I have 2 of these. One in my truck and one in my office.
It is a 24V (40VA) transformer w/ a 3.5 amp circuit breaker. Bought the box from Radio Shack, transformer/circuit breaker from a local hvac supply house, and picked up the #16 wire scrapped on a jobsite. I used an old 12' extention cord I found lying around. It has 4 outlets.

I thought about using a multi-tap transformer(120/208/240/480) and alligator clips in places where a 120v receptacle was not accessable. You could use power from a disconnect both 480/240V. I just haven't gotten around to that yet.JUST BE VERY CAREFUL!

I'm not sure on the power rating of the VAV's but it works on control modules just fine.

You should size your transformer for a 20% safety factor.For example, a 100VA transformer should not have more than 80VA load applied to it.
The VA of the controller should be listed in the controller specifications. Although the ratings can be confusing because they are sometime listed as the maximum VA with loads attached to the controllers. Such as valves and actuators.
Be careful when applying air pressure to the controllers airflow transducers. The pressures from the air flow measuring stations are very low. You will need a special pump to simulate the low pressures.

I need to work out a power solution for the controllers. Please keep in mind that I'm not very familiar with this side of things. Is it possible to use 1 class 2 transformer to power multiple controllers (not all of them, but 2 or 3) and are there any problems that may be associated with doing this? From what I understand, if the controllers have a load of around 20VA each, then a 40 VA transformer could supply 2 controllers. Am I thinking about that correctly? If so, how do I determine what the minimum VA load is for each controller? Would this come from product data / installation manuals?

I just spent 30 seconds doing a Google search and found a half dozen places offering 40-50 VA 24 VAC transformers, modular ... molded boxes that plug directly into standard 120 VAC wall sockets, all going for between 15 and 25 bucks. Of course, I knew such existed because I carry a couple around for various uses. One's with fuses as part of the package. That's pretty cheap and inexpensive. I would NOT mix multiple manufacturer's stuff on the same power supply unless you know more than you obviously do about the subject.

My suggestion, different transformer for each ... or just one transformer, but power only one controller at a time.

Originally Posted by laziboie

Does anyone have any tips or suggestions for what works best when building a board such as this?

Sorry, no. Haven't enough info about what you want to do specifically. Nor about your knowledge or skill level.

Originally Posted by laziboie

Does anyone have any photos of a board in their shop that I could reference (just to get ideas)?

No, sorry. A picture of the boards we have set up in shop for training and application testing wouldn't tell you much that'd be useful. It's far more involved than what you'd need and much of the wiring, etc is not readily visible (it's in snap track).

My suggestion? Keep it SIMPLE. Employ the KISS principle. Nothing more than what you absolutely need to accomplish the goal..

What did you have in mind for an air pump? You do know that 1 PSI is approx 27.7 "WC ... right?

I'd think perhaps a small fan blowing thru small section of duct, with pitot tubes installed MIGHT make a decent simulator. Just hook whichever VAV controller you're working with at the time as needed.

You should be fine as long as you oversize your transformer to make sure you can power any sensors and actuators you may have attached to the controllers. Keep a common "common" across all of them and don't hook up any of them together on any of the inputs/outputs because you don't know what does or doesn't have an isolated power supply and you don't want any inadvertent ground loops. We use 96VA transformer to power 2 or 3 controllers all the time and will even pop a 3 party device on the transformer as long as we have a healthy margin of power left over. I wouldn't go over 90% of rated capacity.

If you are sharing a transformer make sure all the devices are half-wave rectified. If you mix half wave rectified and full wave rectified devices you will be looking for canned smoke on eBay.

kontrol out

"Open is as open does." - Forrest Gump"Can't we all just get a Lon?" - Garry Jack "BACnet: integration or interrogation?" - The Janitor"Open protocols? You can't handle open protocols!" - Nathan R. Jessup“What’s that? Aaa… open protocols? Don’t talk about…. open protocols? Are you kidding me? Open protocols? I just hope we can hardwire an interface!” - Jim Mora http://www.youtube.com/watch?v=U7fjDS0jKiE

You should size your transformer for a 20% safety factor.For example, a 100VA transformer should not have more than 80VA load applied to it.
The VA of the controller should be listed in the controller specifications. Although the ratings can be confusing because they are sometime listed as the maximum VA with loads attached to the controllers. Such as valves and actuators.
Be careful when applying air pressure to the controllers airflow transducers. The pressures from the air flow measuring stations are very low. You will need a special pump to simulate the low pressures.

Thanks for the information! What you mentioned about the transformers make sense. I will look into the specifications for the controllers more to see if I can find this information.

I totally understand that the pressures are typically seen on the transducers are low, but that is a good point to bring up. I was considering some type of regulator or valve on a small 10-gallon fish tank aeration pump that would limit the pressure to a manageable add safe level. Figured I could have a gauge inline.

With an actuator attached to each controller, I was hoping that a valve after the pressure regulator would allow me to adjust the "flow" seen by the controller which would then adjust the actuator. Thought that would be helpful for our guys.

If you are sharing a transformer make sure all the devices are half-wave rectified. If you mix half wave rectified and full wave rectified devices you will be looking for canned smoke on eBay.

kontrol out

Thanks for the tip! I did not realize that was a concern, but it makes sense. I understand the concept and the potential issues associated with this. I assume that you are referring to devices that do not have an isolated rectifier circuit on their power supply. I will follow the manufacturer's guidelines for installation and based on the one's I have seen, they appear to make it very clear when this might be an issue.

I was thinking that I could either 1) have each of the controllers on a separate transformer, 2) provide power to all full-wave devices on one transformer and half-wave devices on another (depending on load of course), or 3) provide some type of external isolation for which I have several options.

All of our VAV installation that do not have line voltage at the controller location (VAV box) use the following power supply in a central location. Generally we limit the number of VAV controllers between 4 and 7 per 100VA circuit, depending on the length of wire to the controller and if it has a reheat valve.

"Open is as open does." - Forrest Gump"Can't we all just get a Lon?" - Garry Jack "BACnet: integration or interrogation?" - The Janitor"Open protocols? You can't handle open protocols!" - Nathan R. Jessup“What’s that? Aaa… open protocols? Don’t talk about…. open protocols? Are you kidding me? Open protocols? I just hope we can hardwire an interface!” - Jim Mora http://www.youtube.com/watch?v=U7fjDS0jKiE

I just spent 30 seconds doing a Google search and found a half dozen places offering 40-50 VA 24 VAC transformers, modular ... molded boxes that plug directly into standard 120 VAC wall sockets, all going for between 15 and 25 bucks. Of course, I knew such existed because I carry a couple around for various uses. One's with fuses as part of the package. That's pretty cheap and inexpensive. I would NOT mix multiple manufacturer's stuff on the same power supply unless you know more than you obviously do about the subject.

I'm not exactly sure what you are referencing...do you mind adding a link to the search or clarifying? I know enough, but I am not going to pretend like I have done this before. Kontrolphreak provided a good explanation about why adding multiple controllers on one transformer might be a bad idea. That is totally the reason I'm asking the questions on this board.

Originally Posted by osiyo

What did you have in mind for an air pump? You do know that 1 PSI is approx 27.7 "WC ... right?

I was thinking of one of the small fish tank pumps with a regulator, valve and gauge that I could use to supply pressure to the transducers. I understand the pressure relationship you described, at the moment, I'm not aware of what the psi rating is on a little fish tank pump but I assume it is near 1 psi. I was definitely keeping this in mind though, but a good point to bring up, thanks!

Originally Posted by osiyo

I'd think perhaps a small fan blowing thru small section of duct, with pitot tubes installed MIGHT make a decent simulator. Just hook whichever VAV controller you're working with at the time as needed.

We are going to have a VAV setup with a controller attached and wanted to do exactly like you have described. I'm not sure how feasible it would be to swap out controllers every time we wanted to test a different system. My main concern would be wiring, space and the fact that some controllers have built in actuators while others are separate. Still, definitely going to do this with at least one controller, a small VAV and a fan. Great idea though, thanks!